This invention relates to valve stem seal assemblies utilized for controlling oil flow between valve stems and valve guide members of internal combustion engines. More particularly, this invention relates to mechanisms for enhancing the control or metering of such oil flow where at least a portion of the stem engaging surface of the seal assembly is threaded.
Internal combustion engines have pluralities of intake and exhaust valves, generally in a one-to-one relationship. Each valve comprises a head and an integral stem reciprocally mounted in a valve guide. Those skilled in the art will appreciate that there must be some oil flow along the stem in order to lubricate the latter as it reciprocates within the guide. As wear occurs in the valve guide and valve stem interface, oil flow will increase, causing excessive oil consumption and the formation of carbon deposits within the combustion chamber.
In order to reduce oil consumption and prevent carbon deposits, as well as to maintain engine performance, various designs have been developed to control or meter the oil flow between the stem and guide members. To the extent that relatively severe operating conditions occur in the exhaust as opposed to the intake valve areas, much effort has been directed to geometries of exhaust valve sealing media.